When Jennifer, at age 33, was diagnosed with MFH sarcoma, a rare type of cancer that originates in the body’s soft tissues, she opted to fight the fight, applying the same sort of focus and discipline that helped her succeed in her career. An avid cyclist, Jennifer and her husband, David, recruited their friends to come together to an indoor cycling event and ride for a cause: to fund research into rare cancers, which surprisingly afflict more than 50% of cancer patients.

Early on, Jen dreamed of raising $10,000. By asking every one of their friends to captain a team – and urging team members to tap their friends for donations — Jen and Dave raised $250,000 in 2007, the launch year. The doctors at New York’s Memorial Sloan Kettering who were working to save Jen’s life were so impressed that they agreed in 2009 to make Cycle for Survival an official MSK fundraiser. Meanwhile Equinox, the chain of upscale health clubs, signed on as a founding partner.

Before she died at age 40 in July 2011, Jen saw Cycle for Survival go national, with events in New York, Chicago and San Francisco. The charity raised $4.7 million that year. That’s an amazing feat, though nothing compared to what the program does today. This past Sunday morning, 16,000 cyclists took part in Cycle for Survival at Equinox clubs in 13 cities across the U.S. Facebook , Blackstone , Piper Jaffray , law firm Akin Gump and executive recruiter Russell Reynolds were among the businesses that had bands of weekend warriors riding to blaring hip-hop. Team DB NYC, representing Deutsche Bank , raised more than $473,000 for cancer. These folks rode at a jam-packed Equinox in Rockefeller Center, where Jen’s mom roamed the gym floor in a blue satin robe and boxing gloves. At noon, Dave Linn, Jen’s husband, triumphantly held up a check for $19.5 million.

That’s how much Cycle for Survival has raised so far this year (you can donate here until April 1). Total money raised since 2007: more than $51 million, making Cycle for Survival the fastest-growing athletic fundraiser in the U.S. (its operators claim) and one that merits more recognition than it’s received. Event sponsors including Coca-Cola’s Smartwater, AOL and News Corp. enable Cycle for Survival to send 100% of its donations to Memorial Sloan Kettering to fund clinical trials and research studies of rare cancers. MSK CEO and president Dr. Craig Thompson told the sweaty hundreds at Rock Center that Cycle for Survival helped create a Center for Molecular Oncology, where researchers profile rare cancers individually to determine what goes wrong in cells, discover new mutations, and ultimately chase a cure.

This year’s riders included a broad range of people impacted by cancer. Equinox President Sarah Robb O’Hagan introduced me to Carla Hassan, PepsiCo’s CMO for the Middle East and Africa region, who came from Dubai with her husband Tariq, an exec at ad giant Omnicom ; they were riding with “Noor’s Army,” a team supporting their six-year-old daughter Noor, who was diagnosed with a rare cancer two years ago and is now in remission. Ethan Zohn, who won $1 million on the third season of CBS’s Survivor and then twice survived Hodgkin’s lymphoma, was there at Rock Center as well. “Cancer doesn’t care who you are, what your goals are, how much money you have or whether you’ve suffered before,” he preached to the Rock Center crowd. “Do you know what a miracle looks like to a cancer patient? Successful research and new drugs.” Zohn went on to say that a new drug emerged just in time to match his exact form of cancer.

Seth Meyers, NBC’s new prince of late-night, was also pumping the pedals at Rock Center—he rides every year as one of Jen’s friends and fans. NBC Universal SVP Brett Goodman, Jen’s brother, says that one of Cycle for Survival’s unexpected benefits is its way of connecting young people to the cancer cause. “Cancer donors are mostly older people,” he explains. “Cycle for Survival brings the age way down. That, to me, is the best part of this. Twentysomethings and thirtysomethings who normally wouldn’t do anything with Memorial Sloan Kettering are sucked in.”

Meanwhile, Dave Linn, 41, juggles his time running Oak Point Partners, an investment firm that he owns with his brother Eric, and building Cycle for Survival in honor of his late wife. Asked if their philanthropic startup is bigger already that he envisioned, he replies, “Oh yeah.” Would Jen be amazed to see what Cycle for Survival has become? “That’s a tougher question,” he says, smiling. “She had big dreams, but I’m pretty sure that this is even beyond what she imagined.”

Watch Jen’s story on Cycle for Survival’s website here. And see her talk about living without fear:

—